More than two dozen foreign oil and natural gas companies are qualified to get in line as Iran's energy sector opens up to investors, the government said.

Sanctions pressure started easing in early 2016 after Iran was confirmed to have met the terms of a multilateral agreement that commits Tehran to stepping away from the technology needed to make a nuclear weapon. The government during the latter half of last year reached preliminary arrangements with several foreign energy companies, including some that have their main business offices in the United States.

SHANA, the official news agency of the Iranian Oil Ministry, released a list of 29 foreign oil and gas companies that are qualified to take part in any upcoming tenders for exploration and production.

According to the National Iranian Oil Co., it's a "big step" in opening Iranian oil and natural gas fields up to Western investors. Iran is the only member of the Organization of Petroleum Exporting Countries that has an allowance for production growth according to a deal reached last year.

Schlumberger, the largest oil- and gas-field services company in the world, is the only one on the list that has offices in the United States. The company in November signed a MOU with the Iranian oil company for data sharing as it relates to work on oil fields straddling the western Iranian border with Iraq.

Most of the 29 companies on the list published by the NIOC are Asian. European players like Austrian energy company OMV and French supermajor Total have also waded into the Iranian energy sector by signing agreements of their own last year.

An overview of the ease of doing business in Iran from the British government finds the Islamic republic is "the biggest new market to enter the global economy" in more than a decade. Some of the sanctions still on the books in the United States complicate financial transactions with Iran and the incoming administration of Donald Trump has expressed reservations about the U.N.-backed agreement that brought sanctions relief to Iran.

An opinion piece published in the Iranian media said Trump has a negative attitude on international bodies like the United Nations.

"In case he opts to keep even 20 percent of his vows in this regard, he will encounter serious challenges in the first phase of his presidency," it read.